This proposal requests continuation funding for a project investigating relationships between cognitive and behavioral flexibility and reinforcement processes. The approach is motivated primarily by an extensive program of prior research from our laboratories at the Shriver Center and behavioral momentum, theory which relates behavioral persistence to the rates of reinforcement signaled by contextual cues. The overall goal of this project is to examine environmental variables that determine behavioral flexibility and to develop a principled, broadly applicable approach to designing behavioral interventions to make adjustments-both increases-in flexibility. Results thus far have shown that: (1) behavioral allocations of individuals with mental retardation conform to relationships predicted by Herrnstein's "matching law" in choice situations; (2) behavioral momentum theory consistently describes the behavior of individuals with mental retardation in laboratory tests; and (3) discriminati on learning procedures designed in accordance with behavioral momentum theory can reduce maladaptive persistence of stimulus control when contingencies changes (e.g., in reversal learning). The specific aims of the continuation project are to conduct basic and applied research that: (1) Documents the extent to which behavioral momentum effects demonstrable in the laboratory will also be found within special-education settings; (2) develops intervention procedures to help individuals with mental retardation respond more effectively in situations that typically occasion distraction or inflexibility in behavioral transitions; (3) Extends functional-analysis diagnostic procedures to include evaluations of behavioral persistence and resistance to change; (4) defines the temporal context in which momentum analyses apply to individuals with mental retardation; (5) applies the principles of behavioral momentum to improve procedures for establishing discrimination skills in individuals with int ellectual disabilities; and (6) compares the effectiveness of momentum-based interventions for behavioral transitions, self-stimulatory behavior, and prompt dependency in individuals who do and do not have autism diagnoses.